Honesty is the point, IMHU, not what it appear, but what it is.

Don't say that it goes well if your players don't know that you have decided
the last enconter to half their level, if you do this will always be a bad
feeling, i think.
You, as DM, must be the first to be honesty, you must be the first to keep
your mind on a realistic plane, you can't do adventure with such devious
objects like half pc's level. IMHO If you as a DM play your good role-play
(You're not going to play the role of a character but the role of the rest
of the universe, but it's the same, you must think like the world and the
world must act like you think, so all is more natural and realistic).

This hated calculation of level and so will only lessen your joy and your
players joy.
If You find them of a level too high for the adventure you have in mind give
less importance on level and more on originality and creativeness.
I think firmly that my job as DM is done when i ask to one of my players
what level is his character and he must go to check it cause he can't
remember. Yes, then i "win" my game. When my players even forget that they
have some numbers to recreate their pc, when all they care for is their

Nadastor, Wizard of the Black Robes
"The power of a man is not in his hands, but in his eyes !
His life is not into his body, but into his mind !
The world is not around him, but is in him !"